Increasing valine, isoleucine, and total branched-chain amino acids for lactating sows.

One hundred eighty-five (n = 24 to 27/group; average parity 1.3) sows (PIC, Line C-15) were used to evaluate effects of the interrelationship between isoleucine and valine on sow and litter performance. Diets were formulated to .90% total lysine with all amino acids other than isoleucine and valine at least 110% of their suggested requirement estimate relative to lysine using ratios derived from the National and Agricultural Research Councils. The control diet was formulated to .50% isoleucine and .72% valine. L-Valine and L-isoleucine replaced cornstarch to provide .72 or 1.07% dietary valine, and .50, .85, or 1.20% isoleucine. A seventh diet contained .50% isoleucine and 1.42% valine. Mean litter size after cross-fostering was 11.1 pigs, and average lactation length was 20.3 d. No valine x isoleucine interactions were observed (P > .10) for most response criteria. Number of pigs weaned (mean = 10.9), sow feed intake (mean = 6.13 kg), and lysine intake (mean = 55 g/d) were not affected by dietary isoleucine or valine. Litter weight and weight gain at weaning increased as dietary valine (P < .07), isoleucine (linear, P < .07), and total branched-chain amino acids (linear, P < .02) increased. Twelve sows per treatment (84 total) were milked manually on either d 17 or 18 of lactation. Increasing dietary valine increased milk DM and fat (linear, P < .01). Milk DM, CP, and fat increased (linear, P < .002) as dietary isoleucine increased. The casein fraction of milk protein increased (linear, P < .01) and whey and nonprotein N fractions decreased (linear, P < .06, P < .01, respectively) as dietary isoleucine increased. Based on these results, valine and isoleucine increased litter weights. The independent increases in litter weaning weights from adding valine and isoleucine suggest separate modes of action in lactating sows.